Operating device for an eletromechanically actuated disk brake

ABSTRACT

The present invention relates to an actuating unit for an electromechanically operable disc brake for automotive vehicles preferably comprising a driving unit ( 1 ) or an electric motor ( 11 ), an actuating element ( 7 ) secured against rotation and causing one ( 4 ) of two friction linings ( 4, 5 ) that are arranged slidably in a brake caliper to move into engagement with a brake disc ( 6 ), as well as a reducing gear ( 2 ) interposed between the electric motor ( 11 ) and the actuating element ( 7 ).  
     To ensure the testability of the reducing gear, the present invention proposes that the means ( 27 ) for providing the anti-rotation mechanism of the actuating element ( 7  or  16,  respectively) be arranged in a gearbox casing ( 24 ) accommodating the reducing gear ( 2 ).

[0001] The present invention relates to an actuating unit for anelectromechanically operable disc brake for automotive vehicles that isarranged on a brake caliper in which two friction linings that cooperatewith each one lateral surface of a brake disc are arranged so as to bedisplaceable within limits, wherein one of the friction linings, bymeans of an actuating element secured against rotation, is directlymovable into engagement with the brake disc by the actuating unit andthe other friction lining is movable into engagement with the brake discby the effect of a reaction force produced by the brake caliper, withsaid actuating unit comprising at least one electric motor and areducing gear interposed between the electric motor and the actuatingelement in terms of effect.

[0002] An electromechanical actuating unit of this type is disclosed ininternational patent application WO 99/42739. The actuating element inthe prior-art actuating unit is formed of the threaded nut of a screwactuator that is used as a reducing gear and has its threaded spindledriven by an electric motor. The anti-rotation mechanism of the threadednut is provided by means of axial extensions inserted into semi-circularopenings of a bearing plate. The bearing plate forms a bearing both forthe threaded nut and the threaded spindle.

[0003] It is disadvantageous in the prior-art actuating unit that thementioned anti-rotation mechanism of the actuating element isinappropriate for a modular design of the actuating unit or,respectively, that the reducing gear employed is untestable. Anothershortcoming must be seen in the comparatively high expenditure, which isespecially due to the costly manufacture of the bearing plate and thethreaded nut. Still another shortcoming presents the risk that the axialextensions get jammed in the bearing plate, in particular in the initialphase of the build-up of the clamping force, with the result of animpaired efficiency.

[0004] Therefore, an object of the present invention is to disclose anelectromechanical actuating unit of the type mentioned hereinabove witha reducing gear that permits independent testing. Another objective isto eliminate the above-mentioned risk of jamming to the best possibleextent and to minimize the axial overall length of the entire actuatingunit.

[0005] According to the present invention, this object is achieved inthat the means for providing the anti-rotation mechanism of theactuating element is arranged in a housing accommodating the reducinggear.

[0006] In a favorable improvement of the subject matter of thisinvention, the means are cylindrical rolls and grooves designed in thehousing or the actuating element, respectively.

[0007] In this arrangement, it is especially advantageous that thecylindrical rolls are retained in a slide bearing that radially embracesthe actuating element.

[0008] In another favorable aspect of the subject matter of the presentinvention, the means is provided by a profiling of the outside surfaceof the actuating element as well as a mating inside profiling of a slidebearing that is unrotatably incorporated in the housing and accommodatesthe actuating element.

[0009] Preferably, the slide bearing includes radial projections beingreceived in recesses or grooves, respectively, designed in the housing.

[0010] In another embodiment of the subject matter of the presentinvention, the profiling of the outside surface of the actuating elementand the inside profiling of the slide bearing are configured as apolygonal profile.

[0011] Further, it is particularly favorable that the reducing gear isdesigned as a screw actuator and that the actuating element is formed ofthe threaded nut of the screw actuator.

[0012] The present invention will be explained in detail in thefollowing description of two embodiments by making reference to theaccompanying drawings. In the drawings,

[0013]FIG. 1 is an axial cross-sectional view of an embodiment of theelectromechanical actuating unit of the present invention.

[0014]FIG. 2 is a simplified view of a reducing gear design that isemployed in the actuating unit of the invention according to FIG. 1.

[0015]FIG. 3 is a simplified view of another embodiment of the reducinggear.

[0016] The electromechanical actuating unit of the invention asillustrated in the drawings is used to actuate a floating-caliper discbrake, with the brake caliper (only represented) mounted in a stationaryholder 29 so as to be slidable. A pair of friction linings 4 and 5 ismounted in the brake caliper so that they face the left and the rightlateral surface of a brake disc 6.

[0017] In the following, friction lining 4 shown on the right hand inthe drawing is referred to as first friction lining, and the otherfriction lining carrying reference numeral 5 is referred to as secondfriction lining. While the first friction lining 4, by means of anactuating element 7, is movable into engagement with the brake disc 6 bythe actuating unit directly, the second friction lining 5 is pressedagainst the opposite lateral surface of the brake disc 6 by the effectof a reaction force generated by the brake caliper when the arrangementis actuated.

[0018] The actuating unit of the present invention which is fitted tothe brake caliper by means of fastening means not shown has a modulardesign and is mainly composed of three independent assemblies ormodules, respectively, namely of a driving unit 1, a first reducing gear2 actuating the friction lining 4, and a second reducing gear 3interposed between the driving unit 1 and the first reducing gear 2 interms of effect.

[0019] The driving unit 1 mentioned above is comprised of an electricmotor 11 which, in the example shown, is a permanent-magnet-energized,electronically commutated motor whose stator 9 is immovably arranged ina motor casing 12 and whose rotor 10 is provided by an annular carrier13 that carries a plurality of permanent magnet segments 14. The firstreducing gear 2 is interposed between the electric motor 11 and theabove-mentioned actuating element 7 in terms of effect and, in theexample shown, is configured as a screw actuator 16 to 18 accommodatedin a part 19, which may also be of integral design with theabove-mentioned brake caliper. In this arrangement, the screw actuatorcomprises a threaded nut 16 and a threaded spindle 17, with severalballs 18 being arranged between the threaded nut 16 and the threadedspindle 17 which circulate upon a rotational movement of the threadedspindle 17 and cause an axial or translatory movement of the threadednut 16. The threaded nut 16 preferably forms the above-mentionedactuating element 7. Further, it can be taken from the drawing that thethreaded spindle 17 driven by the electric motor 11 by way of the secondreducing gear 3 has a three-part design and is comprised of a tubularfirst spindle member 20 which interacts with the threaded nut 16, anannular second spindle member 21, and a third spindle member 22 thatinteracts with the second reducing gear 3. The first spindle member 20defines with the threaded nut 16 spiral-shaped screw thread undercuts 23wherein the balls 18 circulate.

[0020] The arrangement is preferably chosen so that the rotor 10 of theelectric motor 11 drives the spindle member 17 by the intermediary ofthe second reducing gear 3, and the threaded nut 16 is supported on thefirst friction lining 4. The rotor 10 is mounted in two radial bearings8, 15 being arranged in the motor housing 12 or, respectively, in abearing plate 25 that is axially supported on the motor housing 12.

[0021] In the embodiment of the present invention illustrated in thedrawings, the necessary engine torque is reduced by an expedientintegration of a planetary gear 30-34 forming the above-mentioned secondreducing gear 3. The planetary gear, which is interposed between rotor10 and threaded spindle 17 in terms of effect, is comprised of a sunwheel 30 which preferably includes an externally toothed area on rotor10, a plurality of stepped planet wheels, two of which are shown andhave been assigned reference numerals 31 and 32, and a ring gear 33.Ring gear 33 is formed of an internally toothed area of a cover 26 thatrepresents the case of the planetary gear.

[0022] The third spindle member 22 is favorably connected to a planetcage 36 of the second reducing gear 3 by means of a coupling shaft 40.It is especially advantageous that both ends of the coupling shaft 40and the areas of the third spindle member 22 and the planet cage 36receiving these ends are so configured that two universal joints 41, 42develop.

[0023] As may further be seen in FIG. 1, rotor 10 includes a radialcollar 34 carrying components of a position detection system 35 (notshown) that is used to determine the current position of the rotor 10.The position information is then determined by means of a Hall sensor ora magnetoresistive element.

[0024] The above-mentioned screw actuator is preferably incorporated ina bowl-shaped gearbox casing 24 in such a fashion that its threaded nut16 is secured against rotation by appropriate means. The anti-rotationmeans designated by reference numeral 27, is disposed in the area of thegearbox casing 24 close to the first friction lining 4. An elastic sealor sealing sleeve 28 compressed between the threaded nut 16 and thegearbox casing 24 prevents the ingress of contaminants into the interiorof the screw actuator.

[0025] The constructive design of the anti-rotation means 27 becomesapparent from FIG. 2 in particular. It can be seen in the exploded viewthat the threaded nut 16 includes a plurality of axial grooves 43 on itscylindrical surface, while matingly shaped grooves 44 are provided inthe inside wall of the gearbox casing 24. In the assembled condition ofthe screw actuator 16 to 18, grooves 43, 44 accommodate cylindricalrolls 45 that ensure the desired effect and are retained in an annularslide bearing 37.

[0026] In the second design of the reducing gear illustrated in FIG. 3the above-mentioned anti-rotation mechanism is provided by anappropriate configuration of the respective components. For thispurpose, the surface of the actuating element 7 or of the threaded nut160 includes a profiling 38 having a polygonal shape in cross-section.An annular slide bearing 39 with radial projections 46 includes aninside profiling 47 corresponding to the profiling 38, said slidebearing being retained unrotatably in the gearbox casing 240 in theassembled condition. The effect of an anti-rotation mechanism of thistype is fully obvious so that there is no need for explanations.

[0027] List of Reference Numerals:

[0028]1 driving unit

[0029]2 reducing gear

[0030]3 reducing gear

[0031]4 friction lining

[0032]5 friction lining

[0033]6 brake disc

[0034]7 actuating element

[0035]8 radial bearing

[0036]9 stator

[0037]10 rotor

[0038]11 electric motor

[0039]12 motor casing

[0040]13 carrier

[0041]14 permanent magnet segment

[0042]15 radial bearing

[0043]16 threaded nut

[0044]17 threaded spindle

[0045]18 ball

[0046]19 part

[0047]20 spindle member

[0048]21 spindle member

[0049]22 spindle member

[0050]23 screw thread undercuts

[0051]24 gearbox casing

[0052]25 bearing plate

[0053]26 cover

[0054]27 anti-rotation mechanism

[0055]28 seal

[0056]29

[0057]30 sun wheel

[0058]31 planet wheel

[0059]32 planet wheel

[0060]33 ring gear

[0061]34 collar

[0062]35 position detection system

[0063]36 planet cage

[0064]37 slide bearing

[0065]38 profiling

[0066]39 slide bearing

[0067]40 coupling shaft

[0068]41 universal joint

[0069]42 universal joint

[0070]43 axial groove

[0071]44 groove

[0072]45 cylindrical roll

[0073]46 projection

[0074]47 inside profiling

[0075]160 threaded nut

[0076]170 threaded spindle

[0077]240 gearbox casing

1. Actuating unit for an electromechanically actuated disc brake forautomotive vehicles that is arranged on a brake caliper in which twofriction linings (4, 5) that cooperate with each one lateral surface ofa brake disc (6) are arranged so as to be displaceable within limits,wherein one (4) of the friction linings (4, 5), by means of an actuatingelement (7) secured against rotation, is directly movable intoengagement with the brake disc by the actuating unit and the otherfriction lining (5) is movable into engagement with the brake disc (6)by the effect of a reaction force produced by the brake caliper, withsaid actuating unit comprising at least one electric motor (11) and areducing gear (2) interposed between the electric motor (11) and theactuating element (7) in terms of effect, characterized in that themeans (27) for providing the anti-rotation mechanism of the actuatingelement (7 or 16, respectively) is arranged in a gearbox casing (24)accommodating the reducing gear (2).
 2. Actuating unit as claimed inclaim 1, characterized in that the means are cylindrical rolls (45) andgrooves (44 or 43, respectively) designed in the gearbox casing (24) orthe actuating element (2 or 16, respectively), respectively. 3.Actuating unit as claimed in claim 2, characterized in that thecylindrical rolls (45) are retained in a slide bearing (37) thatembraces the actuating element (7 or 16, respectively) in a radialdirection.
 4. Actuating unit as claimed in claim 1, characterized inthat the means is provided by a profiling (38) of the outside surface ofthe actuating element (7 or 160, respectively) as well as a matinginside profiling (47) of a slide bearing (39) that is incorporated inthe gearbox casing (240) secured against rotation and accommodates theactuating element (7 or 160, respectively).
 5. Actuating unit as claimedin claim 4, characterized in that the slide bearing (39) includes radialprojections (46) being received in recesses or grooves, respectively,designed in the gearbox casing (240).
 6. Actuating unit as claimed inclaim 4 or 5, characterized in that the profiling (38) of the outsidesurface of the actuating element (7 or 160, respectively) and the insideprofiling (47) of the slide bearing (39) are configured as a polygonalprofile.
 7. Actuating unit as claimed in any one of claims 1 to 6,characterized in that the reducing gear is designed as a screw actuator(16 to 18), and in that the actuating element (7) is formed of thethreaded nut (16) of the screw actuator (16 to 18).